Originally Posted by
agmetal
Shimano ST-6500s
I would expect those to work.
I can't completely disagree with Ghrumpy's reasoning. I just did some quick measurements, and I have the R559 lever arms as being about 10% longer than the R539s, whereas the reach has increased by around 33%. So you've lost a bit of mechanical advantage. It should still be plenty to achieve the maximum braking your tire traction will allow. You'll just need to squeeze harder than you used to.